Basal Metabolic Rate (BMR) was measured in young subjects with Down Syndrome (DS) and healthy controls to see if extra genomic material affects basal metabolism. No difference was found between DS subjects and controls, suggesting that chromosome 21 does not control BMR. The relation of EEG (electroencephalogram) alpha background to cognitive function and cerebral metabolism was assessed in young and old DS subjects. Old DS subjects with decreased alpha backgrounds had dementia, reduced cognitive function, larger ventricles, and-a global decrease in cerebral glucose utilization compared to age-matched subjects with normal alpha backgrounds. In contrast, the EEG background did not correlate with psychometric or brain metabolic data in the younger DS subjects.